Method of rejuvenating asphalt.



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I JAMES A. W. PINE, OF NEW YORK, N. Y;

METHOD OF REJ'UVENATING ASPHALT.

No Drawing.

This invention or discovery relates to a method of rejuvenating or revitalizing as-' phalt, and particularly lake asphalt, socalled, or asphalt of the type of Trinidad Lake asphalt, wherein the cementitious properties of the bitumen have become exhausted or devitalized or deteriorated through chemical action, or by causes other than injury due to wear and abrasion. Although this invention or discovery relates to the treatment of the asphalt itself, I believe that its most useful application, and perhaps its best expression, is found in the treatment of such asphalt contained in artificial mixtures used for asphalt pavement, and I will therefore address my description to the treatment as applied to such asphalt pavement. It is to be clearly understood however that my invention or discovery is applicable to the treatment of asphalt of said type in and of itself, whether commingled or compounded with other material or not.

In this country the greater part of the asphalt pavement used, approximately 90% thereof, is composed of a concrete mixture in which Trinidad asphalt or asphalt of that type, as distinguished from the rock asphalt commonly used in Europe, constitutes the cementitious material. In making asphalt pavements of this character, which are artificial mixtures, it has been the custom to fuse together refined Trinidad asphalt, orasphalt of that type, with a heavy petroleum residu- ,um in the proportion of about 100 pounds of asphalt to 20 pounds of petroleum residuum.

1 The fusion of these two materials makes an asphaltic cement which is the cementing material that holds together the non bituminous mineral matter, such as sand or'stone dust, in the form of bituminous concrete. It is designed to have about 10% of soluble bitumen in the pavement mixture and the quantity of asphalt cement used depends upon its purity. Asphalt cement composed of Trinidad asphalt and petroleum residuum usually contains about 33% of earthy matter which was originally present in the crude asphalt. The method of manufacturingthis artificial ass Specification of Letters Patent, Application filed August 31, 1908. Serial No, 450,967.

Patented Nov. 2, 190 9.

phalt concreteiis to heat the sand to about 400 F., and to heat the asphalt separatelyin kettles, adding-the fluxing material, such as petroleum residuum, and agitating until a 6. thorough fusion is obtained; then the hot" I sand is dumped into a mechanical mixihgp gj machine-and the asphaltic cement afterwar poured over it while at a temperature of about 300 or 350 F., and by means of agitation each grain of sand becomes coated with the asphaltic cement.v The'mixture so made; is taken to the street and spread whilevhot upon the foundation to the desired'thickness' and rolled with heavy rollers to a smooth and 7 satisfactory surface, and when cold it is ready for tratfic. It has been found that a pavement made in the aforesaid manner. is subject to 'dej terioration by rotting or by-disintegration; or by reason ofchemical'charigesor other; causes resulting in the exhaustion or de-I terioration of the cementitious properties of the bitumen, as distinguished, from injury" 0 due to stress of traflic,wear, improper mixing of the asphaltic mixture, or similar 1 Y causes which do not affect the;inherent cementitious properties of the bitumen. The 1 precise internal character of the exhaustion or deterioration of the as'halt contained" within the mass is difliculii to determine. It is believed that water plays a part in the destructive process; that uricacid pla s a.

part; that illuminatinggas escaping ronr gas pipes below the pavement acts to some-'5 extent as a solvent to destroy thecementitious properties of the bitumen; it is proba able that the presence of salt in-the crude asphalt has some effect in the deteriorating process, and that the use of improper fluxes 9; v

such as petroleumresidues havin aparaflin base, also has a deteriorating effect.- Whatever may be the causefor; causes of the deterioration, disintegrationfor, ex haus- 5, tion, and whatever the precise unascert'ained, chemical change in the structure, the result of the deterioration or exhaustion or. de -1. vitalization of the cemen'ti'tious, properties of the bitumen, is that the asphalt pavement becomes lifeless, crumbly andeasi'ly friable.

The appearance of the exhausted or devitalized asphalt in such deterioratedpavement is that of an inelastic and easily friable mass; itscolor is'dull brown ascontrasted with the brilliant blackof fresh asphalt; and such deterioration of the asphalt pavements usually first exhibits itself in brown patches which quickly go to pieces under the tons of asphalt, have been laidin the cities of the United States during the past thirty years, and that the average life of such pavenient is about ten years.

i The quantity of the exhausted or devitalizedasphalt pavement which is annually thrown away as a waste product as above described has been and is enormous, and it is estimated that not less than one million Square yards of said exhausted pavement is thrown away annually. Several attempts pared material for have been made and processes patented for using old asphalt paving material over again by mixing it with fresh material cou-- taming suflicient new bitumen to furnish the proper cementitions properties for the whole mass, but these attempts have never been practically successful and have never ,been carried'beyond an experimental stage,

and, sofar as I am aware, it has never been proposed before my discovery to revitalize or rejuvenate the exhausted asphalt coutained within said old asphalt paving material, so as to restore its cementitious properties, as distinguished from adding; to such s material fresh asphalt, and so in etlcct' making a new mixture, and using; the old material simply as the non-l'iituminous mineral in redient in place of new sand or the like.

he almost universal practice, prior to my invention or discovery, has been to send the exhausted pavement, which has been taken u in the course of repairs, to the dump, t us wasting it entirely. By the use of my invention or discovery all this exhaustcd and devitalized pavement, which is now thrown away, may be rejuvenated and revitalized without the addition of fresh bitumen or other cementitious material, and restored as often as it becomes exhausted, to a condition equal to or better than fresh preavement construction. Inpracticing the invention 1 subject the mass of-pavcment containing such deteriorated -,or exhausted asphalt, to a tempera ture of between 300. and 400 F. using preferably a temperature of approximately 360 F. under conditions which allow the heat to penetrate uniformly throughout the mass.

assess after while hot. As a result. of this treatment the appearance and quality of the exhausted or devitalizod asphalt changes. it is restored to a bright black color and be comes elastic and tenacious, and the bitumcn recovers its original cemcntilious proper ties. The mass becomes homogeneous and granular as the heated mass is mechanically worked, and in short, the mixture is restored to a condition equal .to or better than thatof the original fresh asphalt mixture, and its substance is indistinguishable either superficially or by analysis from the original mixture prepared from fresh material for pavement construction. Thus, out of a new raw 'material consisting oi. exhausted. crumbly and dcvi'talized asphalt pavement which has heretofore been treated as a waste product having no value whatever, an asphalt mixture. is produced which is in all respects equal to the original mixture, and isfprobably superior thereto owingto the fact that the soluble salt, which'exislcd in the original crude asphalt and which' has a deleterious ell'ect upon the cemcntitious properties of the bitumen, has probably bccome more or less dissolved in use, and also owing, to thc fact that any improper fusion between the asphalt and the fluxes used in theoriginal manufacture of the mixture may be corrected in my process.

it is believed that this process is applicable solely to asphalt; known as lake bit umen, of which 'irinidad asphalt is a type, and to mixtures compounded thereof, and that such asphalt as rock asphalt, which is not subject to internal deterioration or devil alization from the above mentioned causes. and pa vcmcnls composed thereof, would not require, if indeed they were susceptible to, a revitalizating or restorative treatment such as described. .l'lowever, inasmuch as the in tcrnal character of the chemical, changes which bring about the deterioration or de vitalizat-ion of the bitumen is obscure, I do not desire to limit my claim to the treatment of asphalt of the Trinidad type, or of pavements containing the same, although my process is peculiarly, if not exclusively, ap plicablc. thereto.

My invention is applicable to any asphalt which does rot. or d cteriorato by chemical action or from such causes as are above set forth.

I" claim: I l. The method of rejuvenating asphalt, wherein the 1.:c1nen-titious properties of the bitumen have become exhausted ordevital- 'ized 1n whole or inpart through chemical action or by causes other than injury due tov wear or abrasion, consisting in heating a. mass of said 'asphalt to a temperature of between 300 and 400 F. under conditions which allow the heat to penetrate uniformly throughout the mass, whereby the asphalt. is N heating the mass containing the deteriorated cementitious material to a temperature of between 300 and 400 F. under conditions which allow the heat to penetrate uniformly throughout the mass, whereby said material is restored to an elastic and tenacious consistency equal or superior to that of fresh asphalt pavement.

3. The method of rejuvenating asphalt pavement, wherein the cemcntitious properties of the bitumen have become exhausted or devitalized in whole or in part through chemical action or by causesother than injury due to wear or abrasion, consisting in heating the mass containing the deteriorated cementitious material to a temperature of between 300 and 400 F. under conditions which allow the heat to penetrate uniformly throughout the mass, and mechanically agitating the mass while hot, whereby said niaterial is restored to an elastic and tenacious consistency equal or superior to that of fresh asphalt pavement.

4. The method of rejuvenating asphalt pavement, wherein the cementitious proper ties of the bitumen have become exhausted or devitalizcd in Whole or in part through chemical action or by causes other than injury due to wear or abrasion, consisting in heating the mass containing the deteriorated cementitious material to a temperature of between 300 and 400 F. under conditions which allow the heat to penetrate uniformly throughout the mass, and mechanically agitating the mass during said heating process, whereby said material is restored to an elastic and tenacious consistency equal or su pcrior to that of fresh asphalt pavement.

5. The method of rejuvenating artificial asphalt pavement compounded from lake I asphalt wherein the cementitious properties of the bitumen have become exhausted or devitalized in whole or in part through chemical action or by causes other than injury due to wear or abrasion, consisting in heat.- ing the mass containing said deteriorated asphalt to a temperature of between 300 and 400 F. under conditions which allow the heat to penetrate uniformily throughout the mass, whereby said lake asphalt contained within the mass is restored to an elastic and tenacious consistency equal or superior to that of fresh asphalt.

Signed at New York city this 28th day of August 1008.

. JAMES A. W. PINE. Witnesses: V

EUGENE D. ALEXANDER, ERNEST STAUFFEN, J r. 

